Cellulose is a polydisperse, linear chiral homopolymer consisting of regio- and enantio-selective β-1,4-glycosidic linked D-glucose units. Although it contains three different hydroxyl groups at the C-2, C-3, and C-6 positions, hindered dendrons possessing a focal isocyanate moiety were shown to react exclusively at the primary C-6 positions. Therefore, regioselective functionalization of cellulose, i.e. the introduction of either a substituent or more than one substituent onto the cellulose chain at specific hydroxyl group(s), has lead to precisely modified cellulose materials possessing new properties differing from those derived from simple statistical substitution. Regiocontrol within cellulose chemistry leads to the design of advanced material and nano-scale architectures in interdisciplinary research at the interface of organic and supramolecular chemistry. Utilitarian applications of this chemistry are liquid crystalline polymers, host-guest assemblies, sensor matrices, and bioactive materials.
Semiconductor nanocrystals and quantum dots (QDs) have also received great interest from the biological, medical, electronics and other communities. Compared with conventional organic fluorophores, QDs have high luminescence (1 QD=10 to 20 fluorophores), high resistance to photobleaching, narrow spectral line widths, and tunable emission that can be excited using a single wavelength. However, there are a few major considerations in using these nanoparticles in a biological setting, e.g., the aqueous solubility and biocompatibility required for biological applications.